This invention relates generally to packaging machines designed to encase an article, or articles, upon a base pad or substrate in a protective film of theromplastic material by vacuum forming. Machines employing vacuum forming operations to produce such packages have been employed for many years and are generally referred to as "skin-packaging" machines. The product produced on such machines is quite typically structured for mounting on a hook or the like carried by a display board or rack. Such packages are quite typically termed "rack packages".
Typically, prior art apparatus for such skin-packaging has included a vacuum station upon which the substrate is positioned, a thermoplastic film dispensing system arranged to position film over the substrate on the vacuum station, some form of heating element for preheating the thermoplastic film, and a vacuum source for applying vacuum to the substrate to pull the heated film tightly against the substrate around a product resting thereon. Substantially all prior art skin packaging apparatus has provided the functions above set forth. However, the difficulties inherent in properly heating a thin film or thermoplastic material at the appropriate time for forming it about a properly positioned product on a substrate and sequentially performing such operations at a maximum cycle rate has not readily been accomplished and to my knowledge no prior art apparatus has successfully accomplished continuous skin packaging with simple, and relatively inexpensive, apparatus. Apparatus of the type previously known includes, for example, those of my prior U.S Pat. Nos. 3,377,770; 3,534,521; 3,550,348; and 3,587,200, as well as those of others, such as, for example, U.S. Pat. No. 3,204,384 of Donald E. Dallas; U.S. Pat. No. 3,071,905 to Hugh B. Morse, and U.S. Pat. No. 3,676,979 to Thomas L. Schuette.
The prior art patents above mentioned succeed to various degrees in providing continuous packaging operation. They have not, however, provided the extremely simple and almost foolproof operation of the present apparatus nor have they been able to provide the accuracy of sequencing control available in accordance with the present invention.